There are various methods for joining together two workpieces.
For example, two workpieces can be joined together with the aid of supplementary connecting elements. Such supplementary connecting elements can be screws, rivets and the like, for example. Over the years, such supplementary connecting elements have proven to provide a practical connection option in many areas of technology. With respect to the use thereof, these types of supplementary connecting elements have the inherent drawback that a preliminary machining of the workpieces to be joined together is required which, to some extent, can be quite complex (for example, drilling of holes for the rivets/screws), and in that space is required for the supplementary connection elements (for example, projecting screw ends and rivet ends).
Another connection option is to provide the parts to be joined together with a special form design. The form design is selected to maintain or reinforce the connection when the two joined-together parts are loaded in a direction that corresponds to the normal loading of the connection. The two joined-together parts are only separable from one another, if at all, in a direction opposing that of a normal loading of the connection. However, it is also possible to prevent the two joined-together parts from becoming detached even when a load acts on the joint opposite to the usual loading direction. For this purpose, clip-type latching connections can be used, for example. Connection techniques of this kind are normally referred to as form-locking connections.
Connections generally referred to as material-to-material bonds make up another class of possible connection techniques. In these connections, the materials, respectively surface regions in question, are intimately joined together. One differentiates here between joining techniques which provide that the workpieces to be joined together be made of a substantially homogeneous kind of material, and/or have a substantially similar melting point, and those which optionally provide for additionally introducing a joining material made of a substantially homogeneous kind of material, and/or having a substantially similar melting point. In this case, one speaks of welded connections. Welded connections are normally produced by a local heating of the surface regions to be joined to one another. However, there are also cold-welding methods.
When, on the other hand, the materials to be joined together, and/or the optionally, additionally introduced joining material, are dissimilar and/or have significantly different melting points, then one speaks of a brazing or of an adhesive bonding. The term brazing typically applies when a local increase in temperature is used to produce the material-to-material bond of the materials to be joined to one another, thereby melting or softening at least one of the materials used for forming the connection. On the other hand, an adhesive bonding process employs an adhesive in an originally liquid or pasty form. This adhesive is introduced between the workpiece surface regions that are to be joined to one another. There, the adhesive must first cure before load can be applied to the joint. The curing process can be carried out, for example, by the escaping of solvents or by chemical reactions (particularly in the case of multi-component adhesives). Many material pairings also require the use of supplementary adhesion promoters. Moreover, the curing process can be accelerated by employing external measures, such as heating of the adhesive joint, for example.
It is, of course, also customary to combine two or more joining techniques. This makes it possible to combine the various advantages inherent in the concepts of different joining methods.
Although there are significant advantages associated with material-to-material joining techniques, they prove to be problematic for many applications.
For example, adhesive bonding techniques often require relatively long curing times, which can prove detrimental to a speedy and efficient manufacturing of articles. The heating of adhesive bonding regions is often not feasible, since, due to thermal conduction, thermal energy can be conducted into areas where a thermal energy input is problematic.
Also in the case of brazed or welded connections, problems may arise due to thermal conduction into the materials to be joined to one another. This is not only due to an unwanted heating of regions that are located at a distance from the brazed or welded joint. The situation may particularly arise when materials of different thicknesses are brazed or welded, where it is necessary to supply thermal power at significant levels due to the dissipation of heat in the thick material. This can degrade the quality of the brazed or welded joint and, in some instances, lead to damage to the thin workpiece. Therefore, at the present time, materials that differ greatly in thickness are typically not welded or brazed together, and other joining techniques are used alternatively.
Another problem encountered in material-to-material joining methods is that liquid and/or gaseous materials are often released when the material-to-material connection seam is formed. In the case of adhesive agents, for example, such materials can form during the curing reaction due to the gas emission of solvents or the formation of gaseous substances. In the case of brazed or welded connections, such gaseous substances can be formed by the local, typically mostly intense heating of the join regions. This is especially true since, for brazing or welding processes, material mixtures (for example, special metal alloys) are often used, whose purpose is to ensure a most stable and permanent possible connection and/or to lower the melting point or softening point of the material in question. However, there is often a tendency for the fluxing agents used in the process to be released under intense heating. However, in many fields of application, there can be very negative consequences to the release of material. This is because many technical devices have extremely sensitive reactions to impurities. Detector materials, such as those used for radioactive radiation, are mentioned purely exemplarily in this context.
Moreover, WO 95/03555A1 describes a capsule for a detector that functions in an ultra-high vacuum. The gamma spectroscopy detector, which functions in an ultra-high vacuum, is housed in the capsule which has a bakeable getter element to maintain the ultra-high vacuum. The getter element is configured inside of the capsule in a getter sleeve that is separated from the detector by a thermal protection, in order not to damage the detector, which, in particular, can be a germanium detector, during baking of the getter. The thermal insulation of the detector and getter element is realized by a meandering channel configuration between the detector and the getter element. However, it turns out that it is not possible to achieve an adequate pumping capacity through the getter element, particularly under the high vacuum present in a meandering channel configuration. Moreover, as before, the detector is still subject to contamination and damage from particles released from the getter element.